In March 2003, the Italian national anti-terrorism police received an urgent message from the CIA about a radical Islamic cleric who had mysteriously vanished from Milan a few weeks before. The CIA reported that it had reliable information that the cleric, the target of an Italian criminal investigation, had fled to an unknown location in the Balkans.

In fact, according to Italian court documents and interviews with investigators, the CIA's tip was a deliberate lie, part of a ruse designed to stymie efforts by the Italian anti-terrorism police to track down the cleric, Hassan Mustafa Osama Nasr, an Egyptian refugee known as Abu Omar.

The strategy worked for more than a year until Italian investigators learned that Nasr had not gone to the Balkans after all. Instead, prosecutors here have charged, he was abducted off a street in Milan by a team of CIA operatives who took him to two U.S. military bases in succession and then flew him to Egypt, where he was interrogated and allegedly tortured by Egyptian security agents before being released to house arrest.

Italian judicial authorities publicly disclosed the CIA operation in the spring. But a review of recently filed court documents and interviews in Milan offer fresh details about how the CIA allegedly spread disinformation to cover its tracks and how its actions in Milan disrupted and damaged a major Italian investigation.

"The kidnapping of Abu Omar was not only a serious crime against Italian sovereignty and human rights, but it also seriously damaged counterterrorism efforts in Italy and Europe," said Armando Spataro, the lead prosecutor in Milan. "In fact, if Abu Omar had not been kidnapped, he would now be in prison, subject to a regular trial, and we would have probably identified his other accomplices."

Spataro declined to comment on any specifics of the investigation because the case is pending in the Italian courts. The CIA declined to comment.

Since July, prosecutors and judges in Milan have issued arrest warrants charging 22 alleged CIA operatives, including the head of the CIA Milan substation, with kidnapping and other crimes. In interviews and court documents, Italian investigators said they now believe the abduction was overseen by the CIA's station chief in Rome and orchestrated by officials assigned to the U.S. Embassy there.

The case marks the first time that a foreign government has filed criminal charges against U.S. operatives for their role in a counterterrorism mission. In addition to jolting relations between the United States and Italy, normally a strong ally of Washington in the fight against terrorism, the case is fueling a growing chorus of European complaints that the Bush administration has crossed legal and ethical lines in dealing with Islamic extremists.

As investigators in Milan gradually unravel what happened to Nasr, 42, who remains in custody in Egypt, disclosures about the covert operation are causing political problems for both the U.S. and Italian governments.

Italian officials have firmly denied playing any role in the abduction or knowing about it beforehand. But current and former U.S. intelligence officials, speaking on condition of anonymity because they were not authorized to discuss the operation, said the CIA briefed its counterparts at the Italian military intelligence agency ahead of time.

After the case became public, CIA officers involved in the decision to apprehend Nasr told their superiors that the Italian intelligence agency cleared the operation with Italian Prime Minister Silvio Berlusconi. But there appears to be no documentation that would support the claim that he was aware of the case should a public dispute erupt between Italy and the United States, according to two U.S. sources.

Several former intelligence officials said such documentation, on such a sensitive subject, would probably not exist. "The price of doing business is if you get caught, you're on your own," said one former intelligence official.

There are signs that Berlusconi's government has become increasingly uncomfortable with the criminal investigation, which is being carried out by independent judicial authorities in Milan. Prosecutors and judges signed papers last month seeking to compel the United States to extradite the alleged CIA operatives, but Justice Minister Roberto Castelli, a member of Berlusconi's cabinet, so far has not given his approval -- a step that is usually a formality.

After meeting with U.S. Attorney General Alberto R. Gonzales in Washington in early November, Castelli questioned whether the prosecution was politically motivated, calling the lead prosecutor a leftist "militant" whose work needed to be reviewed carefully. Prosecutors have denied any political bias and said they continue to work closely with the FBI on terrorism investigations.

Warnings Are Delivered

One enduring mystery surrounding the case is why the CIA would want to abduct Nasr in the first place.

Italian anti-terrorism police said they were close to arresting Nasr at the time he disappeared. They had him under regular surveillance, with wiretaps on his home telephone, as part of an investigation into a network of Islamic extremists in northern Italy. His disappearance meant that Italian authorities lost a valuable window into the Islamic underground, prosecutors say.

Moreover, Nasr's actions in Egypt complicated their investigations, they say. In April and May 2004, the cleric was heard from briefly when he made a series of telephone calls to family members and acquaintances in Milan. He told them that he had been kidnapped by foreign agents and taken to Cairo, but that he had been released under house arrest after spending more than a year in prison, according to wiretaps of the calls recorded by Italian investigators.

During the telephone conversations, Nasr also warned religious colleagues at a Milan mosque that his Egyptian interrogators wanted to abduct three other people as well, transcripts of the wiretaps show. He was taken back to prison shortly thereafter when Egyptian security officials discovered that he had been in contact with the people in Italy, according to court records.

Mohammed Reda, an Egyptian exile who lives in Milan, told Italian investigators that Nasr warned him on the phone that he was next on the Egyptian government's list of kidnapping targets.

"They told him that sooner or later the same fate would befall the three of us, that they would catch us as soon as possible," Reda told investigators, according to court documents. "They said they had agreements with the Italian authorities that could easily ensure our capture. If we didn't turn ourselves in voluntarily they would kidnap us."

Court records and interviews with Nasr's acquaintances and investigators in Milan suggest that the Egyptian government had wanted for years to capture Nasr, who had been part of an Islamic opposition group. Egyptian authorities had been prevented from capturing him because he had been granted asylum in Italy.

Nasr was wanted by the Egyptian authorities for his involvement in Jemaah Islamiah, a network of Islamic extremists that had sought the overthrow of the government. The network was dispersed during a government crackdown in the early 1990s, and many leaders escaped abroad to avoid arrest. Nasr fled to Albania but also sought refuge in Germany and Bosnia before settling in Italy in 1997.

Arman Ahmed Hissini, the director and imam of the Viale Jenner mosque and cultural center in Milan, was also sought by the Egyptians, court records show. Hissini said Nasr had been afraid for years that the Egyptian security services would come after him even though he was living in Europe.

"He was even afraid to go to Mecca after he got asylum in Italy," Hissini, who is known locally as Abu Imad, said in an interview at the mosque. "He couldn't go out because he was afraid they would catch him."

Scattered Clues

The CIA has an especially close relationship with the Egyptian security and intelligence services.

In May, the New York-based group Human Rights Watch estimated that since 2001, Egypt had worked with other countries to apprehend more than 60 Islamic militants living abroad and return them to Egypt. Soon after, Egyptian Prime Minister Ahmed Nazif told the Chicago Tribune that the CIA alone had handed over to Egypt between 60 and 70 terrorism suspects captured from around the world.

This relationship has led some European counterterrorism officials and outside experts to speculate that Nasr was abducted as a favor to the Egyptian government. But former U.S. intelligence officials said in interviews that the operation was carried out at the behest of the CIA, not Egypt.

They said the kidnapping was the inspiration of the CIA station chief in Rome, who wanted to play a more active role in taking suspected terrorists off the street. CIA officials in Italy came up with a list of three people "they wanted to look at to grab," said one agency official. It is not clear whether Nasr was on the list.

"It was definitely not a favor to the Egyptians," said another intelligence official. CIA officials "had their eye on him."

The Egyptian government has declined to comment on the case. Italian prosecutors said in court documents that they have repeatedly requested information from Egyptian officials but have received no reply.

Investigators said they had uncovered no hard evidence that Egyptian or Italian agents were involved in the abduction, although Nasr later told his family that the two men who seized him spoke "perfect Italian." According to the wiretapped telephone conversations, Nasr claimed that he was tortured by his captors in Egypt -- subjected to freezing temperatures and electric shocks, among other forms of abuse.

Italian police said there were signs that the CIA's substation chief in Milan, identified in court records as Robert Seldon Lady, flew to Cairo shortly after Nasr's disappearance, a trip that many counterterrorism analysts take to mean he took part in the initial interrogation. He spent three weeks there. Lady's attorney has acknowledged in court papers that he is a former CIA officer who worked in Italy for four years while posted at the U.S. Consulate in Milan.

Investigators have seized computer disks from Lady's home outside Milan that show he made travel reservations on a Web site to fly from Zurich to Cairo five days after Nasr disappeared, with a return flight scheduled for three weeks later. Cell phone records also show that calls were placed from Cairo on a telephone believed to be used by Lady during that period, court documents show.

During their search of Lady's home, police found a disk with a digital photograph of Nasr, showing him walking along the same block in Milan where he was abducted a month after the picture was taken.

Lady, who retired from the CIA a year later, is one of the 22 alleged CIA operatives who have been charged with kidnapping in the case. He has hired an Italian defense attorney, who recently filed a motion to have the charges against him thrown out.

The attorney, Daria Pesce, argued that the evidence seized at Lady's home was obtained illegally. She said he has not admitted or denied playing any role in the case but is actively contesting the charges. She said in a telephone interview that naming him publicly would not jeopardize his former status as an undercover officer or pose security concerns.

"We're just telling the judge that they don't have any evidence that he could have kidnapped" Nasr, Pesce said. "There could never be a trial against him in the United States with such lousy evidence."

Last week, Italian Judge Enrico Manzi disagreed with Pesce. In a written opinion upholding the arrest warrant, the judge wrote that the evidence taken from Lady's home "removes any doubt about his participation in the preparatory phase of the abduction."